Glencross was born December 28, 1982, in Kindersley, Saskatchewan, but grew up in Provost, Alberta.[1] He is the son of Mel and Robin Glencross, and has a younger brother, Matthew, and sister, Kari.[2] His parents both played hockey and say he inherited an intense competitive nature from them.[2] His family moved to Red Deer, Alberta when he was a teenager as his parents began a livestock auction business.[2] Glencross was small for his age, standing less than five feet tall when he was 15, and as a result was often left off the top teams in minor hockey despite having the talent to play; he played Midget C hockey in Provost.[1] He experienced a rapid growth spurt, growing a full foot in a period of 17 months, and was recruited to play Junior A hockey for the expansion Brooks Bandits of the Alberta Junior Hockey League (AJHL) in 2000.[2] He went on to become the first Bandit alumnus to play in the National Hockey League (NHL),[3] and his number 17 was retired by the team in 2011.[4]

The Bandits were a last-place team both years Glencross played, but he was among the AJHL's leading goalscorers in 2001–02 with 42 goals. He went undrafted by an NHL team, but received interest from National Collegiate Athletic Association (NCAA) schools and was considering returning to Brooks for a third season of junior. Jack Kowal, assistant coach of the University of Alaska-Anchorage Seawolves, had scouted Glencross during the season. Impressed with his ability and intensity on the ice, offered Glencross a full scholarship to play for his school.[2] Glencross played two seasons at Alaska-Anchorage between 2002 and 2004, scoring 32 goals and 57 points in 72 games.[5] He was named the Western Collegiate Hockey Association offensive player of the week for December 15, 2003, after scoring a hat trick against the Colorado College Tigers in a 5–2 win.[6][7] He led the Seawolves in goals (21) and points (34) in 2002–03.[8]

Glencross chose to forgo his final two years of college eligibility, signing a professional contract with the Anaheim Mighty Ducks on March 25, 2004.[5] He was assigned to the team's American Hockey League (AHL) affiliate, the Cincinnati Mighty Ducks, to complete the 2003–04 season. He scored two goals in seven regular season games, and one more in nine playoff games.[8] He remained with Cincinnati in 2004–05, appearing in 51 games and scoring nine points.[5] He was moved to the Portland Pirates, also of the AHL, in 2005–06 and improved to 15 goals and 25 points in 41 games while also appearing in 19 post-season games.[5]

Glencross' 2006–07 season was split between four teams. Glencross began with the Pirates, but at mid-season earned his first call-up and made his NHL debut on January 13, 2007.[9] He scored his first goal that night, against Peter Budaj, in a 3–2 loss against the Colorado Avalanche.[10] He played two games with Anaheim before he was traded, along with Zenon Konopka and a 7th round draft pick, to the Columbus Blue Jackets in exchange for Mark Hartigan, Joe Motzko and a 4th round pick on January 26.[5] Glencross appeared in seven games with the Blue Jackets but finished the season in the AHL with the Syracuse Crunch.[8]

Glencross served as an alternate captain for the Flames.

Glencross established himself as an NHL regular in 2007–08. He appeared in 36 games for the Blue Jackets before being traded to the Edmonton Oilers in exchange for Dick Tarnstrom on February 1, 2008.[11] Glencross appeared in 26 games for the Oilers, scoring 15 goals and 25 points in 61 games combined between Columbus and Edmonton.[5] Though he played well with Edmonton,[12] the Oilers did not make a contract offer, making him an unrestricted free agent.[13] Glencross hoped to remain in Edmonton as it was close to his Red Deer home. But after the Oilers made little effort to negotiate with him, he chose to sign a three-year, $3.6 million deal with Edmonton's provincial rival, the Calgary Flames.[14]

In his first year with the Flames, Glencross set new personal highs in games played (74), goals (13) and points (40).[8] He missed six games in December 2008 with a knee injury,[9] and three more early in the 2009–10 NHL season after he was suspended for a blind-side hit on Chris Drury of the New York Rangers.[15] He set a new personal best with 15 goals on the season that included his first NHL hat trick in a victory over the Carolina Hurricanes.[16] His season was ended on March 17 after suffering a leg injury when he was struck by Matt Hendricks of the Colorado Avalanche in a knee-on-knee collision.[17]

Playing in the final year of his contract, Glencross set personal highs of 24 goals and 43 points in 2010–11.[18] While the Flames received offers from other teams for Glencross at the trade deadline, the team chose to hold on to him though they risked losing him as an unrestricted free agent following the season.[19] Glencross chose to remain in Calgary, agreeing to a four-year, $10.2 million contract with the Flames on May 17, 2011. Glencross felt that he could have earned a bigger contract on the open market, but chose to take less money to remain in Calgary.[18] With 26 goals in 2011–12, Glencross finished second on the team to Jarome Iginla's 32. He was the league's most efficient scorer, scoring on 23.6 percent of his shots on net.[20]

Glencross reached several milestones in the lockout-shortened 2012–13 season en route to leading the Flames with 15 goals. After scoring his 100th career goal, he recorded both his 100th assist and 200th point in a 5–4 victory over the Phoenix Coyotes on February 24, 2013.[21] His season was ended prematurely by a knee injury after Anaheim's Ben Lovejoy stuck his leg out to cause a knee-on-knee collision. The injury forced Glencross out of the team's final four games of the season.[22]

Injuries plagued Glencross throughout the 2013–14 season as he missed 15 games to a sprained knee, then suffered a high ankle sprain three weeks after his December 10 return.[23] The injury forced him out of the lineup for nearly three months; he missed an additional 29 games before returning to action.[24] In just the sixth game after his return, he scored his third career hat-trick in an 8-1 victory against the Edmonton Oilers.[25]

Glencross and his wife Tanya have two daughters.[29] An active member of the community, Glencross serves as a spokesman for the Special Olympics program,[30] and hosts an annual charity golf tournament in support of Calgary Crime Stoppers.[31] The first event, held in 2009, raised C$100,000.[32] Glencross is also involved with the Alberta Children's Hospital. In recognition of his community efforts, the Flames named him the 2012 recipient of the Ralph T. Scurfield Humanitarian Award, given by the team in recognition of on-ice leadership coupled with community service.[33]